1. Field of Invention
This invention relates to seatbelt systems and more particularly to seatbelt systems which include a means for locking the passenger restraining belt during a vehicular emergency.
2. Prior Art
Seatbelt systems restrain passengers during vehicular emergencies by fastening a passenger restraining belt around the passenger and anchoring the ends of the belt to the vehicle body to thereby prevent the passenger from colliding with dangerous objects. Furthermore, in order to prevent any interference of the passengers freedom of movement under normal vehicle operating conditions, at least one end of the belt is anchored to the vehicle body via a retractor mechanism which power retracts the belt. The retractor mechanism includes an inertial locking mechanism which abruptly stops the extension of the belt only during a vehicular emergency. The inertial locking mechanism includes ratchet wheels which are coupled to a retractor shaft which retracts the end of the belt. During a vehicular emergency, a pawl which is actuated by an acceleration sensing device is caused to engage with the ratchet wheels. This action stops the rotation of the retractor shaft so that the belt cannot be extended from the retractor mechanism.
In such retractor mechanism, however, even though rotation of the retractor shaft in the direction of belt extensions immediately stops when a vehicular emergency occurs, the belt wound around the retractor shaft in successive layers continues to be extended until the layers of the belt are wound in tight contact with each other; i.e. the belt is tightened down on the retractor shaft. Accordingly, the restraint of the passenger is incomplete and as a result the safety of the passenger cannot always be guaranteed.
To overcome this problem seatbelt systems have been proposed; however each of such seatbelt systems has its own disadvantages and shortcomings.